A rongeur is a surgical tool used to remove a small volume of tissue. One type of rongeur is a Kerrison rongeur. At its most basic, a Kerrison rongeur consists of a static outer tube in which an inner tube, called a cutting tube, is slidably disposed. A plate is disposed over the distal end of the outer tube. The outer tube is also formed with a side opening immediately proximal to the plate. The distal end of the cutting tube is open. The cutting tube is formed so as to have either a cutting edge or cutting teeth that extend circumferentially around the open end of the tube. A rongeur is used to remove tissue by positioning the tubes so that the tissue to be removed protrudes into the outer tube through the side opening. The cutting tube is brought forward to excise from trapped tissue from the adjacent tissue. A rongeur has proven to be a useful surgical tool because the only tissue that is subject to removal is the tissue within the outer tube. This substantially reduces the likelihood that nearby tissue not intended for removal inadvertently comes into contact with the teeth or cutting edge of the cutting tube.
It is known to further provided a rongeurs with a suction connections to the proximal end of the cutting tube. This arrangement allows a suction to be drawn through the cutting tube. This suction draws away the tissue as the tissue is separated from the adjacent tissue. This eliminates the need for the practitioner to, after each bit of tissue is cut, remove the rongeur from the site at which it is applied, remove the cut tissue and then reposition the rongeurs so a new section of tissue can be removed.
One type of rongeur is a rongeur that is purely manually actuated. To use this type of rongeur, the practitioner manually reciprocates the cutting tube back and forth to cut the tissue targeted for removal. Typically the rongeur includes a lever arm that is pivotally connected to the inner tube. The practitioner repetitively moves this lever arm back and forth so as to induce a like movement of against the tissue targeted for removal. A disadvantage of this type of rongeur is that the practitioner is required to use muscles power to perform the whole of the cutting process. Having to repetitive use muscles to both hold the rongeur steady and reciprocate the cutting tube against tissue that is resistant to cutting can fatigue the hand and fore arm. This is especially true if the rongeurs is being used repeatedly to remove a number of different sections of tissue.
To remedy this problem, powered rongeurs have been proposed. This type of rongeur includes a handpiece to which a motor is slidably mounted. The cutting tube extends from the motor. The outer tube is static relative to the handpiece. A linkage system allows the practitioner to move the motor relative to the handpiece. This results in the like movement of the distal end of the cutting tube relative to the outer tube. When tissue is to be removed using this type of rongeur, the motor and cutting tube are advanced distally forward so the cutting edge/teeth is/are forced against the tissue to be removed. The motor is actuated. The rotation or oscillation of the motor results in the like movement of the cutting edge/teeth against the tissue. This movement, in combination with the force placed on the teeth by the practitioner results in the severing of the target tissue.
An advantage of the above device is that it eliminates the need for the practitioner to have to repetitively employ muscle power to force the cutting of the target tissue by the rongeur. However, a limitation of this device is that it only allows the motor system to perform the cutting of the tissue to which it is applied. There are number of procedures for which the practitioner may want to switch between using manual force and the supplied powered force to cut the tissue against which the rongeurs is applied. For example, when the rongeur is spaced from tissue it is important not be cut, the practitioner may decide that, to speed the procedure and minimize muscle fatigue, it is useful to use the supplied force, the motor force, to cut the tissue. Then, as the rongeur approaches tissue that it is important not be cut, the practitioner may want to rely solely on manual force to perform the cutting. This manual force while slower than the powered force, allows would provide the practitioner more control than would be obtained by rely on mechanical force to overcome the resistance of the tissue to being cut.
Another reason a practitioner may want to interleave the use of manual and mechanized forces to cut the tissue is that the resistance to which the practitioner is exposed by using manual force to cut the tissue can provide feedback regarding the condition of the tissue and/or the cutting process.
Also, a further disadvantage of known motorized rongeurs is that the practitioner is required to use muscle force to press both the cutting tube and associated motor against the target tissue. During the severing process it is desirable to only apply a select amount of force longitudinally against the tissue being removed. With the described type of device, the practitioner is required to apply manual force that holds both the cutting tube and the attached motor against the tissue. This may make it difficult for the practitioner to precisely control the extent to which the cutting tube is pressed against the tissue. For example, if the rongeur is directed downwardly, gravity may apply a force against the motor that also urges the cutting tube against the tissue. In this situation, the practitioner must adjust the force he/she applies to compensate for the added gravitational force that is also urging the cutting tube against the tissue. Alternatively, if the rongeurs is directed upwardly, gravity may work to force the cutting tube away from the tissue against which the tube is to be applied. This can require the practitioner to use apply more force than he/she might normally use in order to press the tube against the tissue to be removed.